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How to cut moist air issues in blasting

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article image Using a dehumidifier allows better control over the tank job

During any tank job, the newly blasted surface is required to be left unpainted overnight or over a weekend. The presence of moisture in the air can cause flash rust and spoil the ready blasted surface, making it unpaintable.

Using a dehumidifier on the tank project can help the user blast all day and hold the blast that night or longer to avoid having to clean up the spent abrasive, rush the paint job and clean the equipment, or put a holding primer on the surface.

Those working on tank jobs can hold the blasted condition of the steel for days, when the containment and dehumidification are correctly monitored and controlled. This allows the work to be conveniently stopped in the middle if required, without any worries about losing the blast to flash rusting and forfeiting the hours of work and materials already spent.

Using a dehumidifier allows better control over the tank job, resulting in quality. To maintain correct conditions in the tank, four air changes of dehumidified air per hour are required in the tank. For instance, if the tank has a capacity of 60,000 cubic feet, a 4,000 cfm dehumidifier will be required.

Reduce the water content in the air with a dehumidifier

Dehumidification is not about just heating the air or reducing the relative humidity (also known as the ‘RH’). Simple heating will only allow the air with lower RH to hold more water before saturation, with no water being actually removed. Dehumidification effectively reduces the actual water content in the air by removing it.

Surface preparation

The RH factor during abrasive blasting and immediately after can make the substrate surface vulnerable to corrosion such as flash rusting. The electrolyte in atmospheric corrosion is usually the water in the air. Introducing dehumidified air into an enclosed work area will reduce the RH significantly. If the humidity is reduced to below 50% RH, one can effectively ‘hold the blast’ on uncoated, blasted steel for days or weeks; this also means that one can even blast non-stop for a week before having to stop, clean up and paint, improving the production cycle.

Drying

Dehumidifiers can be used in the construction industry to save time and money, especially by drastically reducing the curing of concrete floors and walls prior to painting. Painting schedules for indoor or undercover work need not go off-track due to wet weather conditions as dehumidified air reduces drying time of paint. An optional precooler is also available, which lowers surface temperatures to assist with the curing process of the applied coating. The precooler is a fatigue management tool that maintains workable conditions for workers in the area.

Preservation

A dehumidifier can be effectively used near equipment such as boilers during maintenance. Dry air from the dehumidifier will protect equipment during any scheduled maintenance process.

Power it with propane

If the dehumidifier’s heaters are operated on propane instead of electricity, costs can be reduced by thousands of dollars per month. Though the motors and controls will continue to operate electrically, the bulk of the energy required to operate the dehumidifier is consumed by the heaters.

Contact a BlastOne / Blastmaster dealer for more information.

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